Of the three diets—standard low fat, ultra low carb, and low glycemic—the amount of calories

The results were impressive. Those on the "Atkins" diet burned 350 calories more per day - the equivalent of an hour of moderate exercise - than those on the standard low-fat diet. Those on the low-glycemic diet burned 150 calories more, roughly equivalent to an hour of light exercise.

While the ultra low carb, Atkins-like diet had the greatest initial effect, it also had the lowest, long-term retention rate. On top of that, it increased the risk of heart problems. Although the low glycemic index diet didn't offer the same calorie-burning advantages, there were no adverse effects and it was easier to maintain over time. The key point of interest here, however, is that despite the same calorie intake, more calories were burned by altering the types of foods those calories came from. Reducing carbohydrates—especially of the processed variety—had a distinct effect on fat retention, metabolism, and overall health. While no single study is definitive proof of the inequality of calories, it suggests some good advice when considering your next diet: avoid processed foods, eat healthy, and be patient.

For more details, be sure to read the entire article over at the New York Times.